Studies link childhood lead exposure, violent crime

Antonio Perez, Chicago Tribune

City inspector Paul Diaz talks to a 2-year-old whose blood was found to contain lead at four times the federal standard. Increasingly, researchers are finding lead poisoning at a young age is linked to permanent changes in the human brain that may increase criminality.

City inspector Paul Diaz talks to a 2-year-old whose blood was found to contain lead at four times the federal standard. Increasingly, researchers are finding lead poisoning at a young age is linked to permanent changes in the human brain that may increase criminality.

The toxic legacy of lead gets new attention as a factor in urban violence, troubled schools

After growing up poor in a predominantly African-American neighborhood of Cincinnati, the young adults had reached their early 20s. One by one, they passed through an MRI machine that displayed their brains in sharp, cross-sectioned images.

For those who had been exposed to lead as toddlers, even in small amounts, the scans revealed changes that were subtle, permanent and devastating.

The toxic metal had robbed them of gray matter in the parts of the brain that enable people to pay attention, regulate emotions and control impulses. Lead also had scrambled the production of white matter that transmits signals between different parts of the brain, largely by mimicking calcium, an element that plays a critical role in brain development.

Scars left by lead have had significant consequences for the study participants and their communities. As children, they struggled in school more than those who had not been exposed. As teens, they committed crimes more frequently, University of Cincinnati researchers reported.

"What we found — and continue to find — is that lead sowed the seeds of their future," said Kim Dietrich, a neuropsychologist who has been following the group of nearly 300 people since they were born in the late 1970s. "It isn't conducive to behavior we associate with normal development, making smart decisions and success."

People have known for centuries that lead is poisonous, and removing it from gasoline and paint has dramatically reduced exposure for American children.

But a growing body of research is making it clear that the toxic legacy of lead has far more wide-ranging effects than previously known. Lingering dust from paint and deposits from old vehicle emissions continue to harm thousands of children in older industrial cities like Cincinnati and Chicago.

Once an obscure academic specialty, lead poisoning is gaining new appreciation from economists, criminologists and education experts as researchers document how early exposure harms children in ways that don't become apparent until years later. The damage ends up costing taxpayers in the form of increased spending on health care, special education and law enforcement.

Last month, a Tribune investigation found that lead hazards are festering in the same parts of Chicago that have given the city a national reputation for violence and academic failure. In impoverished, crime-ridden neighborhoods like Austin, Englewood and Lawndale, more than 80 percent of the children tested in 1995 had dangerous lead levels.

Today those kids are in their early to mid-20s, when criminal behavior peaks.

As evidence mounts of the links between lead poisoning, poor school performance and crime, some scientists are starting to focus on lead pollution as a key factor in Chicago's violence.

Tribune Graphics

Tribune Graphics

"People in neighborhoods like Englewood have faced multiple assaults over different periods of time — job losses, segregation, housing discrimination," said Robert J. Sampson, a Harvard University researcher who has been studying Chicago for more than two decades. "Yet through all of that there is this persistent lead poisoning. It creates a social context where kids are at a clear disadvantage."

Sampson recently added lead data to his existing research on poverty, education and crime in Englewood and other neighborhoods. The results, he said, were shocking. A map of lead poisoning rates among children younger than 6 in 1995, for instance, looks very similar to a map of aggravated assault rates in 2012, when those kids were 17 to 22 years old.

"It's not something I appreciated before," Sampson said. "But when I see the astounding levels of lead poisoning in these communities, it makes complete sense that it is part of the cycle of deprivation."

Politicians and policymakers have yet to catch up to this line of thinking, seemingly regarding lead pollution as a problem solved long ago. During the past five years, federal and state officials have sharply cut funding to screen kids, inspect properties and eliminate lead hazards.

With less money directed at the problem, children ages 5 and younger continue to be harmed at rates up to six times the Chicago average in corners of predominantly African-American neighborhoods on the South and West sides, according to the Tribune's analysis of city records.

One researcher working in Chicago, Anne Evens, recently published a study that draws a sharper focus on how lead is still ravaging the city years after it faded as a local and national issue.

A former chief of lead poisoning prevention at the Chicago Department of Public Health, Evens obtained the lead tests of more than 58,000 children born in the city from 1994 to 1998 and compared the results with how they performed on standardized tests in third grade.

Her peer-reviewed study, published in April in the scientific journal Environmental Health, found that exposure to lead during early childhood significantly increased the chance that a student would fail reading and math tests, even when controlling for other factors such as poverty, race, birth weight and the mother's education level.

The scope of what Evens found is staggering: At three-quarters of Chicago Public Schools, the average lead level of third-graders exceeded a standard established by the Centers for Disease Control and Prevention in each year from 2003 to 2006.

Why is third grade so important? That's when children begin to use reading to learn other subjects, and studies show students who fail to master reading skills during such a critical year are more likely to fall behind in later grades and drop out of high school. Dropouts are significantly more likely to end up in jail than to get a diploma.

Some teachers and reading specialists know that kids exposed to lead as toddlers are more likely to act out, have trouble staying on task and struggle to work well with classmates. Yet it doesn't come up in the debate about how to improve schools.

"I used to think that lead was only a problem years ago for kids who had eaten a bunch of paint chips," said Karl Androes, co-founder of Reading In Motion, a nonprofit that trains CPS teachers to improve reading skills in kindergarten and first grade through music and drama. "That's also why we've had trouble getting the (education) foundations or the principals to pay attention to it."

"But we're talking about our kids now," Androes said. "And there just isn't enough attention being paid to how lead affects the classroom."

Even modest reductions in lead exposure can make a difference.

Jessica Wolpaw Reyes, an economist at Amherst College, studied what happened during the 1990s when Massachusetts embarked on an effort to eliminate lead paint hazards in homes with young children. She found the $5 million-a-year program helped reduce the number of students who performed poorly on standardized tests by 1 to 2 percentage points, with most of the benefits seen among children from low-income communities.

While that might not sound like much of an improvement, Reyes said, it was equivalent to what the state could have expected if it had closed the income gap between poor and middle-income communities by 22 percent.

"There is a lot of research showing if you can intervene early with children, it costs relatively little but makes a huge difference," Reyes said. "Yet that's a hard sell to policymakers. It's tough to get people to spend money on things that aren't going to yield benefits for another 15 or 20 years."

Multiple studies have concluded that steps taken to reduce lead exposure already have saved money, with the value of removing the toxic metal from gasoline estimated in the billions or trillions of dollars. Some, including Reyes, argue that stopping the constant flow of lead into the environment is a major reason why crime rates dropped sharply nationwide during the 1990s.

In a 2007 paper, Reyes traced how the 1970 Clean Air Act kicked off the decline in the use of leaded gasoline. The rate of decline varied widely among states and tracked almost perfectly with state-by-state drops in violent crime rates about 20 years later.

Similar studies have been conducted by Rick Nevin, a consultant to the U.S. Department of Housing and Urban Development, and Tulane University researcher Howard Mielke, whose earlier work helped lay the foundation for the phaseout of leaded gasoline.

They concluded that steps taken to reduce childhood lead exposure were a major factor — if not the biggest factor — in preventing people from committing violent crimes in their early 20s.

"This is a no-brainer for the public health community, which is very familiar with what lead does to the human brain," said Reyes. "But until recently, police chiefs and the criminology community in general have been very skeptical."

At a recent City Club of Chicago breakfast, a moderator said he was "going on a limb" in asking Chicago police Superintendent Garry McCarthy about the connection between lead exposure and violent crime. Audience members reacted with laughter.

"Yeah, I kind of study this stuff," said McCarthy. "I don't know."

The moderator quickly moved on to another subject. McCarthy declined to comment for this story.

One of the most compelling Chicago-related studies explored the lead-crime connection at the city level. Mielke, along with colleague Sammy Zahran, compared leaded gasoline emissions with aggravated assault rates in Chicago and five other cities and found a good fit in each one.

Both trends look like an upside-down "U." Emissions from leaded gasoline started increasing in the 1950s, peaked in the early '70s and then steadily declined. Aggravated assault rates rose, peaked and fell on a similar curve, only about 20 years later.

As these studies have percolated beyond scientific journals, the biggest dispute appears to be on how much of an impact the decline of lead had on crime rates. Other experts credit changes such as falling unemployment rates, more police on the streets, higher rates of incarceration and a shift away from the use of crack cocaine.

University of Chicago economist Steven Levitt, co-author of the best-seller "Freakonomics," cited the legalization of abortion as a big part of the crime drop. Fewer unwanted babies, he has argued, meant fewer violent young men decades later.

"The vast majority of people still dismiss lead as anything of any consequence," said Bruce Lanphear, a researcher at Simon Fraser University in Vancouver who conducted some of the first research on health effects at low doses. "It's almost impossible to separate out the underlying reasons for these problems, but lead certainly is one of things that triggers urban decay."

The link between childhood lead exposure and violent behavior is well-established, both in animal research and human studies like the one in Cincinnati. Small doses can reduce IQ and essentially cause parts of the brain to short out, in particular the areas responsible for controlling aggression.

Given the scale of lead hazards in Chicago, advocates say political leaders are overlooking a cost-effective way to help improve schools and reduce crime.

"Of all the problems that affect kids in these neighborhoods, lead is the easiest to solve," said Evens, who now heads Elevate Energy, a nonprofit that addresses lead issues while making homes more energy-efficient. "But there just isn't the political will to do something about it."